Definitions of irregular migrants are problematic and complex, for reasons discussed in detail in the CLANDESTINO methodological report. For the sake of approximate comparability among countries, two broad types of irregularity have been distinguished in the database: irregular foreign residents (IFR) and irregular foreign workers (IFW).
- IFR are foreign nationals without any legal resident status in the country they are residing in, and persons violating the terms of their status so that their stay may be terminated.
- IFW are foreign nationals working in the shadow economy, including those with a regular residence status who work without registration to avoid due taxes and regulations.
The following graph shows the main overlaps and differences between the two groups, ignoring the fact that semi-compliance may blur some of the differences in reality.
The more intensely coloured fields indicate the overlap between the two categories: adult foreign nationals who work in unregistered jobs, either without any residence status or on short-term, non-working visas (working tourists). They are likely to constitute the majority of all irregular residents in most EU countries.
In addition, IFR include foreign nationals without any residence status who do not work: children, aged and unemployed persons. Foreign nationals with falsified papers who are registered and seemingly legal for the authorities are usually not covered in estimates of IFR.
While the irregularity of the residence is the main criterion for IFR, the irregularity of work is decisive for IFW. Persons without legal residence status who are employed in regular, tax-paying jobs are usually not covered by estimates aiming at irregular work. On the other hand, IFW estimates include persons who are legally present in the country and perform irregular work. These are mainly three groups:
- EU citizens who are working in the shadow economy.
- Third country nationals with a right to stay who work in spite of having no right to work (e.g. asylum seekers).
- Third country nationals who have a right to stay and work, but who are working in the shadow economy, avoiding due taxes and regulations.